Download A Closer Look at Some Hormones 1. Melatonin $ produced by

A Closer Look at Some Hormones
1. Melatonin
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produced by pineal gland, located deep in brain
is non-steroid (protein-based)
causes sleepiness
as daylight fades, levels rise
linked to sleep disorders and SAD (seasonal affective
disorder)
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decreased light levels in
winter cause symptoms of
depression and urge to sleep
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treated by light therapy
Ideas to ponder:
- what about shift work and melatonin levels?
- how common is SAD in Canada?
2. Thyroxine
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produced by the thyroid gland (in neck)
is non-steroid (protein) and has iodine in it
increases metabolic rate
increases oxygen consumption by stimulating
Na+/K+ pumps in target cells, which of course,
requires O2
gives off heat
Thyroxine, like many other hormones, works on a negative feedback
loop. This means it works in conjunction with another hormone. High
levels of TSH from the pituitary gland stimulates the thyroid gland to pick up
iodine from the blood and make thyroxine for secretion. As the levels of
thyroxine increase in the blood, it suppresses TSH from being released by the
pituitary gland. Thyroxine levels will later drop, causing a increase in TSH
and so on.
They work together, when one is high the other is low and they cycle
back and forth, thereby maintaining homeostasis.
Medical complications involving thyroxine:
Excessive thyroxine (Hyperthyroidism):
 causes Graves Disease. Antibodies attach to TSH receptors on thyroid
cells. This makes the thyroid gland think there are always high levels of
TSH, so it keeps on producing thyroxine results in:
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enlargement of thyroid
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muscle weakness
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increased metabolic rate
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excessive heat
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increased appetite
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weight loss
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poppy eyes
Hypothyroidism (myxedema)
 can be caused by iodine deficiency. There is continued production of
TSH, but little thyroxine can be produced
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lowered metabolism
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always cold
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decreased heart rate
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weight gain
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no appetite
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weakness
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fatigue
When infants are born with hypothyroidism, it will cause permanent
developmental delay if untreated before the age of two months. Infants are
always tested for this shortly after birth.
Goiter - not enough iodine in the diet can cause a huge swelling of the
thyroid gland. This disease is rare now because of the addition of iodine in
table salt (See freaky picture on page 433)
3.
Adrenaline and noradrenaline (aka epinephrine and norepinephrine)
These two hormones are slightly different but act the same
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often called the stress hormone
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involved in fight or flight
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secreted by the inner layer of the adrenal
glands - called the medulla - adrenal
glands sit on top of the kidneys
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regulated by the hypothalamus
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both hormones are also excitatory
neurotransmitters in the sympathetic
nervous system (explains why they have
a quicker affect than other hormones)
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increase blood pressure
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increase heart rate
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cause vasodilation - widening of the
blood vessels - in heart and lungs
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release glucose from liver into
bloodstream
Adrenaline is used in EpiPens . A severely allergic reaction called
anaphylactic shock can result from exposure to antigens. This exposure
triggers the release of massive amounts of histamine. Histamines cause
blood pressure to drop, and results in reduced blood and oxygen flow in the
body. Since adrenaline causes an increase in heart rate, proper blood
pressure can be restored.
4.
Human Growth Hormone (HGH)
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also called somatotrophin
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non- steroid hormone
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produced by the anterior pituitary gland
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only remains active in body for 20 hourstriggers release of growth factors by liver
to prolong the effects
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responsible for body growth
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increases calcium absorption
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increases cell division
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increases cell development
(Especially in bone and cartilage)
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stimulates protein synthesis
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stimulates lipid metabolism
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decreases with age
Medical Complications related to HGH
Hypersecretion: often caused by a pituitary tumour. The effects
differ depending on when the hypersecretion happens:
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prior to puberty - giantism - abnormally
long bones (picture p 429)
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after puberty- acromegaly - thickening
of bone tissue causing abnormal growth
of head, hands and feet (picture p 430)
Hyposecretion - causes pituitary dwarfism, abnormally short but
with normal body proportions. Genetic dwarfism is totally different.
Pituitary dwarfism may result from a pituitary tumour or no pituitary
gland at all. Puberty may be delayed or never occur at all. (See picture
page 429) Treatment today is with genetically engineered bacteria that will
produce HGH for human use.
Ideas to ponder:
should doctors make HGH available to shorter than average children?
should HGH be available to older adults looking to slow the aging
process, like facelifts and other cosmetic surgery is available now?